1. Field of the Invention
The present invention relates to masking materials for use in plasma etching, and more particularly to masking materials for applications in plasma etching of silicon and silicon-containing materials using chlorine and fluorine -based plasmas.
2. Description of Related Art
Plasma etching techniques using species produced from chemically inert and chemically active gases have many industrial uses, including notably in the fabrication of integrated circuits. Chemical plasma etching equipment includes barrel etchers, parallel plate etchers, and reactive ion etchers. Chemical plasma etching processes rely exclusively or to a substantial degree on excited gas species that are suitable for reacting chemically with the material to be etched, although in some cases sputtering of the masking material and/or material being etched can occur depending on the molecular weight of the impinging gas and the molecular weight of the material exposed to the impinging gas. For example, chloride-based and fluorine-based plasmas have been successfully used in the etching of photoresist-masked silicon, silicon dioxide, silicon nitride, aluminum and tungsten.
Patterned plasma etching involves the use of a masking material having a significantly slower etch rate in the plasma than the etch rate of the material being etched. Masking material should also be easy to apply and distribute across the material being etched, and easy to strip after etching is complete. Unfortunately, the photoresist masking material in common use in the semiconductor industry is subject to chemical attack by chlorine-based and fluorine-based plasmas. While erosion of the masking material is tolerable in many process applications, the erosion is excessive in such applications as deep trench fabrication requiring lengthy exposure of the wafer to the plasma. Hence, a masking material that can be readily applied and distributed across a wafer or other body and easily patterned and easily stripped, but that is relatively impervious to certain commonly used plasmas is desirable.